September in Cayo Largo is the rainiest month of the year. In September, the weather in Cayo Largo is typically hot. Average daily high temperature in September is about 29 degrees above zero. On average, Cayo Largo has 18 rainy, 10 sunny, 1 cloudy, and 1 partly cloudy day in September. The rains are usually heavy. September as well as June, August, and October is considered the most uncomfortable time to visit Cayo Largo.